The present invention relates, in general, to package inspection systems, and more particularly to high speed systems for sensing and evaluating the integrity of a package, rejecting those packages which do not meet specifications, obtaining data on sensed package parameters, and evaluating the data to determine error rates and trends.
Commercial packaging machinery, including machines which package products such as cigarettes, routinely operates at very high speeds, and a single machine may produce in excess of 700 packages per minute. Such packages may include a number of packaging elements which must be accurately assembled to produce a commercially acceptable product These elements include, in the case of a cigarette package, for example, a foil wrapper layer, an outer packaging envelope, and a closure stamp which is attached to two opposite sides of the packaging envelope and which extends across an exposed portion of the foil wrapper layer. Similar elements can be used in other packages, but for convenience of reference, the present invention will be described in terms of a conventional cigarette package. It will be understood, however, that the invention has application to any package made up of plural elements which must be present and properly aligned to produce a marketable packaged product.
Considerable attention has been directed, in the past, to the development of methods and machines for measuring and evaluating the integrity of the various elements in a multi-element package structure, for it is highly desirable that each package be consistent in its exterior appearance with other such packages, and that all of the packages be uniform in their exterior dimensions. Cigarette packages, for example, include printed labels on the outer packaging, and the positioning of the printing on such labels must be accurate and consistent. The packages also carry closure stamps which must be centered on the package and aligned with the label and with the printing on the label. Furthermore, the outer packaging envelope should be consistently positioned with respect to the foil wrapper layer so &hat a consistent amount of the foil is exposed above the packaging envelope. Other package parameters which should be detectable by a package inspection system include package end flaps which have not been properly closed, girth seams or wrappings which are loose or not completely sealed, misaligned printing, and other such defects. Because these parameters must be measured in a high production environment, the inspection system must be capable of operating at a high speed as well, so as not to slow down package production. In addition, inspection systems must be substantially insensitive to random or stray effects such as uneven spacing of the product as it leaves the packaging machine, stray light reflections from glossy package surfaces, and similar effects which are inherent in a production line
One attempt to overcome the problems experienced with high speed package inspection systems involved the use of a conveyor apparatus having a pair of laterally spaced endless belt conveyors which engage the top and bottom ends of a package to move it through an inspection station. The belts are driven by pulleys which are driven from a single shaft. This shaft carries a coded disc which rotates in synchronism with the drive belt. A photocell detects the motion of the coded disc and provide spaced output signals corresponding to specified intervals of motion of the drive belts so that a count of these signals specifies the position of the package carried by the belts. The conveyor belts tightly engage the packages to be monitored so that the location of the package is accurately synchronized with belt motion. Electro-optical scanners are positioned along the path defined by the conveyor belts to sense predetermined patterns and characteristics on the package and to compare signals produced by the scanners with signals stored in memory to determine whether the packages were properly made. If package errors are detected, a reject signal directs the package to a rejection chute. However, such a system depends on precise positioning of the package in the conveyor belts, and does not allow for slippage or variable spacing between packages, since it relies upon a coded disc which is remote from the package actually being inspected.
Inspection systems have also been provided for individual articles, such as cigarettes, where each cigarette is tested for a specific characteristic and articles not having the required characteristic are rejected. Typically, such systems require a timing mechanism which is synchronized with the movement of the articles to generate timing pulses for use in operating the system. Again, however, maintenance of synchronization between the articles, the sensing apparatus, and the reject apparatus presents problems, and any uneven spacing of the product can produce undesired results.
Numerous patents have issued which disclose inspection systems for packages and in particular for cigarette packs which utilize detectors for locating defective packs and for producing reject signals. Photosensitive detectors have been provided for determining whether a pack has a tax label, for example, or whether each cigarette in a row includes the required filters. Other patents have suggested the use of photocells to inspect the sealed edge of a wrapper, and guide rails, guide brushes, and the like have been used to keep the packages to be inspected on a conveyor. However, continuing problems have been encountered in obtaining accurate and reliable measurements of package characteristics so that packages which do not meet specifications can be rejected, and such problems are particularly acute in high speed measurement systems where timing and synchronization problems become most apparent.
Because of the stringent requirements for consistent, uniform packages to meet high quality control standards for packaging machines, there is a definite need in the packaging art for an improved package inspection system, including both method and apparatus, which is capable of detecting various package elements, evaluating the measurements, and identifying selected packaging defects on a high-speed processing line so that substandard packages can be ejected from the line. Such a system should provide data relating to the numbers and types of defects which can be stored and evaluated to enable operators of the system to locate sources of problems and to detect trends which might indicate potential problems in the production line so that faults can be anticipated and corrections can be made in the process control to maintain the flow of product.